Group transfer processes for acrylic star polymers

ABSTRACT

Large acrylic star polymers, are made by group transfer polymerization techniques by arm-first, core-first, or arm-core-arm approaches.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in part of U.S. application Ser. No. 627,919,filed July 5, 1984, abandon.

BACKGROUND 1. Preparation of Hydrocarbon Star Polymers

Star polymers derived from unsaturated hydrocarbon monomers, such asstyrene, butadiene and isoprene, have been obtained by preparinglithium-terminated "living" polymers via anionic polymerization and thencoupling the "living" polymer chains by reacting them with variouspolyfunctional linking agents. This has usually produced hydrocarbonstar polymers with relatively few (3-12) arms. Hydrocarbon star polymerswith a larger number of arms (e.g., 15-56) have been obtained bysequential anionic polymerization of difunctional monomers (e.g.,divinylbenzene) with monofunctional monomers (e.g., styrene) or withmonomers that behave as monofunctional monomers (e.g., isoprene). Bothmethods of preparing hydrocarbon star polymers have benn reviewed by B.J. Bauer and L. J. Fetters in Rubber Chem. and Technol. (Rubber Reviewsfor 1978). Vol. 51, No. 3, pp 406-436 (1978).

A Aoki et al., U.S. Pat. No. 4,304,881 (1981), preparedstyrene/butadiene "living" polymers by anionic polymerization and thencoupled them by reaction with silicon tetrachloride to poduce a 4-armstar polymer having a silicon core in Example 4.

H. T. Verkouw, U.S. Pat. No. 4,185,042 (1980), prepared a polybutadiene"living" polymer by anionic polymerization and then prepared asilcon-containing 3-arm star by reacting the "living" polymer withγ-glycidoxypropyltrimethoxysilane in Example 5.

R. Milkovich, U.S. Pat. No. 4,417,029 (1983), prepared a hydrocarbonstar polymer having 10 arms of 2 kinds. Of the 10 arms, 5 were a diblockcopolymer of polystyrene (Mn=12,300) and polyisoprene (Mn=52,450). Theother 5 arms were polyisoprene (Mn=52,450). The hydrocarbon star polymerwas prepared by charging sec-butyllithium, then isoprene, them more seebutyllithium, then isoprene, then divinylbenzene at a mole ratio ofdivinylbenzene to sec-butyllithium initiator of 5.5:1. Subsequentreaction of the "living" lithium sites in the core with carbon dioxideor ethylene oxide produced carboxylic acid or hydroxyl groupsrespectively in the core in Example 2.

T. E. Kiovsky, U.S. Pat. No. 4,077,893 (1978), suggested reactinglithium-terminated "living" polymers derived from diene monomers (e.g.,butadiene or isoprene) with divinylbenzene to form a 4-25 arm starpolymer and then reacting the (still living) star polymer with the sameor a different monomer to grow further polymer chains from the core.Thus, star polymers having two kinds of arms were proposed in Col. 5,lines 40-58.

W. Burchard and H. Eschway, U.S. Pat. No. 3,975,339 (1976), reacted amixture of 50% divinyl-benzene and 50% ethylivinylbenzene in toluenewith n-butyllithium to produce a polydivinylbenzene microgel having 270active lithium-carbon bonds per molecule. This was subsequently reactedwith styrene to produce a star polymer having 270 arms, each arm havinga weight average molecular weight of 17,500 in Example 1.

H. Eschway, M. L. Hallensleben and W. Burchard, Die MakromolekulareChemie, Vol. 173, pp 235-239 (1973), describe the anionic olymerizationof divinylbenzene using butyllithium to produce soluble "living"microgels of high molecular weight. These microgels were then used toinitiated polymerization of other monomers to produce star polymers. Thenember of arms depended on the number of active sites in the "living"microgel, which in turn depended on the mole ratio of divinylbenzene tobutyllithium initiator. To avoid gellation it was necessary to work atlow concentrations (e.g., 2.5% in benzene).

H. Eschway and W. Burchard, Polymer, Vol. 16, pp 180-184 (March, 1975),prepared a star polymer having 67 polystyrene arms and 67 polyisoprenearms by sequential anionic polymerization of styrene, divinylbenzene andisoprene. Low concentrations of monomer were used to avoid gellation.

2. Preparation of Acrylic Star Polymers

In contrast to hydrocarbon star polymers (which may be prepared havingdifferent arm sizes, different numbers of arms and even with twodifferent kinds of arm attached to the same core), acrylic star polymershave been available only in a limited variety of structures.

G. W. Andrews and W. H. Sharkey, U.S. Pat. No. 4,351,924 (1982),prepared acrylic star polymers having 3 or 4 hydroxyl-terminated arms bycoupling acetal-ended, "living" poly(methyl metharylate) with 1,3,3-tris(bromomethyl) benzene of 1,2,4,5-tetrabis (bromomethyl) benzene.

O. W. Webster, U.S. Pat. Nos. 4,417,034 (Nov. 22, 1983) and 4,508,880(Apr. 2, 1985), and W. B. Farnham and D. Y. Sogah, U.S. Pat. Nos.4,414,372 (Nov. 8, 1983) and 4,524,196 (June 18, 1985) showed thatacrylic star polymers can be prepared via group transfer polymerizationby coupling "living" polmer with a capping agent having more than onereactive site or by initiating polymerization with an initiator whichcan initiate more than one polymer chain. Initiators that could produceacrylic star polymers with up to 4 arms were demonstrated.

R. J. A. Eckert, U.S. Pat. No. 4,116,917 (1978), describing hydrocarbonstar polymers suggested that small amounts of other monomers (e.g.,methyl methacrylate) may be included (Col. 3, lines 22-28) and thatethylene dimethacrylate may be used as a coupling agent (Col. 5, lines22-28). A similar suggestion is made by T. E. Kiovsky, U.S. Pat. No.4,077,893, cited above.

J. G. Zilliox, P. Rempp and J. Parrod, J. Polymer Sci., Part C, PolymerSymposia No. 22, pp 145-156 (1968), describe the preparation, viaanionic polymerization, of a mixture of star polymers having 3 to 26polymethyl methacrylate arms attached to cores of ethylene glycoldimethacrylate. The mixture also contained linear polymethylmethacrylate. The article says the lengths of the individual brancheswere constant by that the number of branches per star "fluctuatesconsiderably", giving rise to a very high polydispersity.

3. Uses of Star Polymers

Hydrocarbon star polymers have been used as additives to improve theimpact strength of polyphenylene ether resins--W. R. Haaf et al., U.S.Pat. No. 4,373,055 (1983); dry nylon--W. P. Gergen et al. U.S. Pat. No.4,242,470 (1980); rubber-modified polystyrene--A. Aoki et al, U.S. Pat.No. 4,304,881, cited above; and chlorinated polyvinyl chloride resins M.H. Lehr, U. S. Pat. No. 4,181,644 (1980).

Hydrocarbon star polymers have also been added to asphaltic concrete toimprove the service life--C. R. Bresson, U.S. Pat. No. 4,217,259 (1980);to polyetherester resins to provide a desirable overall balance ofproperties-R. W. Seymoure, U.S. Pat. No. 4,001,286 (1977), and tolubricating oil to improve the viscosity index and act as adispersant--T. E. Kiovsky, U. S. Pat. No. 4,077,893 (1978).

Hydrocarbon star polymers have also been used to prepare thermoplasticshaving good clarity by blending them with thermoplastic resins such asmethyl methacrylate/styrene/butadiene copolymers, polyester urethanes,epoxides, acrylics, polycarbonates, polyesters, etc.,--E. L. Hillier,U.S. Pat. No. 4,048,254 (1977).

Acrylic star polymers, because of the limited selection heretoforeobtainable, have not been put to as great a variety of uses.

SUMMARY OF THE INVENTION

Group transfer polymerization processes are provided for preparingacrylic star polymers which comprise.

a. a crosslinked core comprising a polymer derived from a mixturecomprising

i. 1-100% by weight of a monomer having at least two carbon-carbondouble bonds polymerizable by a group transfer polymerization processand optionally

ii. 0-99% by weight of a monomer having one carbon-carbon double bondpolymerizable by a group transfer polymerization process,

b. attached to the core, at least 5 arms comprising polymer chainsderived from one or more monomers polymerizable by a group transferprocess, and

C. attached to the core or to at least some of the arms, "living" grouptransfer polymerization sites.

These processes comprise: an arm/core process comprising

a. preparing a "living" polymer by reacting a group transfer initiatorwith one or more monomers having a carbon-carbon double bondpolymerizable by a group transfer polymerization process;

b. attached to the core, at least 5 arms comprising polymer chainsderived from one or more monomers polymerizable by a group transferprocess, and,

a core/arm process comprising

a. preparing a "living" core by reacting a group transfer initiator witha mixture comprising

i. 1-100% by weight of a monomer having at least two carbon-carbondouble bonds polymerizable by a group transfer polymerization processand optionally,

ii. 0-99% by weight of a monomer having one carbon-carbon double bondpolymerizable by a group transfer polymerization process;

b. contacting the resulting "living" core with one or more monomershaving one carbon-carbon double bond polymerizable by a group transferpolymerization process.

and an arm/core/arm process comprising

a. preparing a "living" polymer by reacting a group transfer initiatorwith one or more monomers (A) having a carbon-carbon double bondpolymerizable by a group transfer polymerization process;

b. contacting the resulting "living" polymer with a mixture (B)comprising

i. 1-100% by weight of a monomer having at least two carbon-carbondouble bonds polymerizable by a group transfer polymerization processand optionally

ii. 0-99% by weight of a monomer having one carbon-carbon double bondpolymerizable by a group transfer polymerization process to produce a"living" star polymer having "living" group transfer polymerizationsites in the core and,

c. contacting the resulting "living " star polymer with one or moremonomers (C) having one carbon-carbon double bond polymerizable by agroup transfer polymerization process, where the monomers (C) can be thesame as or different from the monomers (A).

By these processes, acrylic star polymers can be provided which comprise

a. a core comprising a polymer derived from a mixture comprising

i. 1-100% by weight of one or more monomers, each having at least twogroups, ##STR1## ii. 0-99% by weight of one or more monomers, eachhaving one group, ##STR2## b. attached to the core, at least 5 armscomprising polymer chains derived from one or more monomers, each havingone group, ##STR3## in each of which R is the same or different and isH, CH₃, CH₃ CH₂, CN or CO₂ R' and Z' is O or NR', wherin R' is C₁₋₄alkyl.

wherein: at least 50% of the molecules of such star polymer have from atleast 5 to 2,000,000 arms. preferably at least 50, more preferably atleast 100 arms. In a preferred embodiment, such arms are of 1 or moresets of different types, wherein:

i. the polymer chains comprising one of the types of arms have the sameor different molecular weight and are derived from the same or differentmonomers as the polymer chains comprising the other said type of arms,

ii. the polymer chains comprising each type of arms have an armpolydispersity of 1.0 to 2.0 where said arm polydispersity is the weightaverage molecular weight divided by the number averager molecular weightof the polymer chains of that type, and

said star polymers, comprising both core arm of 1 or more types, have amolecular polydispersity of 1.0 to 2.0, wherein said molecularpolydispersity is the weight average molecular weight divided by thenumber average molecular weight of the molecules.

This can be described as a bimodal or polymodal narrow polydisperisty,wherein each of the star polymer itself and the arms or separate sets ofarms have narrow polydispersities.

Also, preferably the star polymer of this invention is a soluble acrylicstar polymer comprising

(A) a crosslinked core comprising a polymer derived from a mixturecomprising

(i) 1-100% by weight of one or more monomers, each having at least twogroups, ##STR4## (ii) 0-99% by weight of one or more monomers, eachhaving one group ##STR5## b. attached to the core, at least 5 armscomprising polymer chains derived from one or more monomers, each havingone group, ##STR6## in each of which R is the same or different and isH, CH₃, CH₃ CH₂, CN or CO₂ R' and Z' is O or NR', wherein R' is C₁₋₄alkyl, wherein: at least 50% of the molecules of such star polymers havea least from 5 to 2,000,000 arms. wherein the ratio of the number ofarms to the number of difunctional acrylic repeat units in the core isless than or equal to 1:1.

Such star polymers are made using a polymerization initiator in a molarratio of initiator to difunctional acrylic monomer of less than or equalto 1:1, giving a crosslinked core and not gelling the reaction mixture.By "soluble" is meant that nothing separates out from a solution of 1%by weght stars in 99% solvent (toluene, glyme and/or THF) uponcentrifuging at 17,00 rpm for 30 minutes. Preferably the arms solubilizethe core.

Such star polymers of a variety of types are provided that have usefulproperties for applications in coatings, films, fibers and plasics. Thestar polymers comprise (1) a core derived from a multifunctional monomerhaving at least two polymerizable double bonds, (2) at least 5 polymericarms attached to the core and preferably (3) "living" group transfersites on the core and/or on the arms.

Such "living" star polymers comprise

a. a crosslinked core comprising a polymer derived from a mixturecomprising

i. 1-100% by weight of a monomer having at least two carbon-carbondouble bonds polymerizable by a group transfer polymerization processand optionally

0-99% by weight of monomer having one carbon-carbon double bondpolymerizable by a group transfer polymerization process,

b. attached to the core, at least 5 arms comprising polymer chainsderived from one or more monomers polymerizable by a group transferprocess, and,

attached to the core or to at least some of the arms, "living" grouptransfer polymerization sites.

Preferably, in star polymers of the invention, the monomers having onecarbon-carbon double bond polymerizable by a group transferpolymerization process are selected from ##STR7## and mixtures thereofwherein: X is --CN, --CH═CHC(O)X' or --C(O)X':

Y is --H, --CH₃, --CN or --CO₂ R, provided, however, when X is--CH═CHC(O)X', Y is --H or --CH₃ ;

X' is --OSi(R¹)₃, --R, --OR or --NR'R"; each R¹ is independentlyselected from C₁₋₁₀ alkyl and C₆₋₁₀ aryl or alkaryl;

R is C₁₋₂₀ alkyl, alkenyl, or alkadienyl; C₆₋₂₀ cycloalkyl, aryl,alkaryl or aralkyl; any of said groups containing one or more etheroxygen atoms within alophatic segments thereof; and any of all theaforesaid groups containing one or more functional substituents that areunreactive under polymerizing conditions; and each of R' and R" isindependently selected from C₁₋₄ alkyl

More preferably, "living" acrylic star polymers of the inventioncomprise

a. a core comprising a polymer derived from a monomer mixture comprising

1-100% by weight of a monomer having at least two carbon-carbon doublebonds polymerizable by an initiator, Q-Z, and optionally

ii. 0-99% by weight of a monomer having one carbon-carbon double bondpolymerizable by an initiator, Q-Z, and

b. attached to the core, at least 5 arms comprising polymer chainsderived from one or more monomers polymerizable by an initiator, Q-Z,and

c. attched to the core and/or to at least some of the arms the groupsQ-Z"-.

where the group Q- is the initiating moiety in a "living" group transferpolymerization initator, Q-Z, and where the group Z"- is derived from anactivating substituent, Z, of a group transfer polymerization initiator,Q-Z, and where the initiator, Q-Z, is capable of reacting with a monomerhaving carbon-carbon double bonds to form A "living" polymer chainhaving the group, Z"-, attached to one end of the "living" polymer chainand the group, Q-, attached to the other, "living", end of the "living"polymer chain and where, the "living" polymer chain is capable ofinitiating polymerization of additional monomer, which can be the sameor different from the monomer used to prepare the "living" polymerchain, to produce a larger "living" polymer chain having a group, Z"-,attached to one end of the "living" polymers chain and the group, Q-,attached to the other "living" end of the "living" polymer chain, andwhere the group, Z"-, is the same as or an isomer of the group, Z-.

Also preferably in the preparation of star polymers of the invention,the "living" group transfer polymerization sites are (R¹)₃ M- wherein:R¹ is selected from C₁₋₁₀ alkyl and C₆₋₁₀ aryl or alkaryl; and M is Si,Sn, or Ge.

Still more preferably, in polymer of the invention, the group, Q-, is(R¹)₃ M- as defined above.

In such polymers, the group, Z-, is selected from ##STR8## and mixturesthereof wherein: X' is OSi(R¹)₃, --R, --OR or --NR'R"; each R¹ isindependently selected from C₁₋₁₀ alkyl and C₆₋₁₀ aryl or alkaryl;

R is C₁₋₂₀ alkyl, alkenyl, or alkadienyl; C₆₋₂₀ cycloalkyl, aryl, alkarlor aralkyl; any of said groups containing one or more ether oxygen atomswithin aliphatic segments thereof; and any of all the aforesaid groupscontaining one or more functional substituents that are unreactive underpolymerizing conditions; and

each of R' and R" is independently selected from C₁₋₄ alkyl

each of R² and R³ is independently selected from H; C₁₋₁₀ alkyl andalkenyl; C₆₋₁₀ aryl, alkaryl, and aralkyl; any of said groups except Hcontaining one or more ether oxygen atoms within aliphatic segmentsthereof; and any of all the aforesaid groups except H containing one ormore Functional substituents that are unreactive under polymerizingconditions; and

Z'is O or NR';

m is 2, 3 or 4;

n is 3, 4 or 5.

DETAILED DESCRIPTION OF THE INVENTION

In the preparation of the star polymers, use is made of "group transfer"polymerization. By "group transfer" polymerization, is meant apolymerization process in which polymerization of monomers havingcarbon-carbon double bonds is initiated by certain initiators of theformula Q-Z where Z is an activating substituent that becomes attachedto one end of the growing polymer molecule and where Q is a group thatcontinuously transfers to the other end of the growing polymer moleculeas monomer is added to the growing polymer molecule. Thus,polymerization of the monomer, ##STR9## initiated by a group transferinitiator, Q-Z, proceeds as follows: ##STR10## The group, Q, is thus anactive site that can initiate further polymerization of more monomer.The polymer molecule having the group, Q, is referred to as a "living"polymer and the group, Q, is referred to as a "living" group transferinitiating site.

The word "living" is used sometimes herein in quotation marks toindicate its special meaning and to distinguish it from substances whichare alive in a biological sense.

More particularly, in the preparation of the star polymers, use is madeof the "group transfer" polymerization process of the gerneral typedescribed in part by W. B. Farnham and D. Y. Sogah, U.S. Pat. No.4,414,372 and by O. W. Webster, U.S. Pat. No. 4,417,034, and incontinuation-in-part U.S. Pat. Nos. 4,508,880 Webster, granted Apr. 2,1985, and 4,524,196 Farnham and Sogah, granted June 18, 1985, thedisclosures of all of which are incorporated herein by reference. Grouptransfer polymerization produces a "living polymer" when an initiator ofthe formula (R¹)₃ MZ is used to initiate polymerization of a monomerhaving a carbon-carbon double bond.

In the initiator, (R¹)₃ MZ the Z group is an activating substituent thatbecomes attached to one end of the "living" polymer molecule. The (R¹)₃M group becomes attached to the other ("living") end of the "living"polymer molecule. The resulting "living" polymer molecule can thenitself act as an initiator for polymerization of the same or a differentmonomer to produce a new "living" polymer molecule having the Zactivating substituent at one end and the (R¹)₃ M group at the other("living") end. The "living" polymer may then be deactivated, ifdesired, by contacting it with an active proton source such as analcohol. At this point, it might be useful to consider a specificexample--the group transfer polymerization of specific monomer (in thiscase, methyl methacrylate) using a specific group transfer initiator (inthis case 1-trimethylsiloxy-1-isobutoxy-2-methylpropene). The reactionof 1 mole of initiator with n moles of monomer produces "living" polymeras follows: ##STR11## The ##STR12## group shown on the left side of the"living" polymer molecule is derived from the activating group, z,which, in the initiator, was in the form ##STR13## The--Si(CH₃)₃ groupon the right side ("living" end) of the "living" polymer molecule is the(R¹)₃ M group. The "living" polymer molecule can act as an initiator toinitiate polymerization of the same or a different monomer. Thus, if theabove "living" polymer is contacted with m moles of butyl methacrylatein the presence of active catalyst, the following "living" polymer isobtained: ##STR14##

If the resulting "living" polymer is then contacted with methanol, thefollowing deactivated polymer is obtained. ##STR15##

The star polymers of the invention are prepared by three differentmethods, each making use of the group transfer process described above.

(1) Arm-First Method

In this method, a "living" polymer (the arm) is prepared by contacting amonomer (A) having a carbon-carbon double bond with a group transferinitiator, (R¹)₃ MZ. The resulting "living" polymer is then contactedwith a multifunctional linking agent (monomer B) having at least twopolymerizable double bonds per molecule of linking agent. This producesa star polymer having arms of polymerized monomer A attached to acrosslinked core of polymerized monomer B. The active group transfersites in the core can be deactivated by reaction with a proton source.

(2) Core-First Method

In this method, a "living" core is prepared by contacting a grouptransfer initiator, (R¹)₃ MZ, with a multifunctional linking agent(monomer B) having at least two polymerizable double bonds per moleculeof linking agent. The resulting "living" core is then contacted with amonomer (A) to produce a star polymer having arms of polymerized monomerA attached to a crosslinked core of polymerized monomer B. The activegroup transfer sites at the ends of the arms can be reacted with afurther monomer or deactivated by reaction with a proton source.

(3) Arm-Core-Arm method

In this method, a "living" polymer (the first arm) is prepared bycontacting a monomer (A) having a carbon-carbon double bond with a grouptransfer initiator, (R¹)₃ MZ. The resulting "living" polymer is thencontacted with a multifunctional linking agent (monomer B) having atleast two polymerizable double bonds per molecule of linking agent. Thisproduces a star polymer having arms of polymerized monomer A attached toa crosslinked core of polymerized monomer B and having "living" grouptransfer sites in the core. This is then contacted with a third monomerC to grow arms out from the core. The monomersA and C can be the same ordifferent and the number of moles of A and C can be the same ordifferent. Thus, if desired, the two types of arms can have differentmolecular weights and/or be derived from different monomers. Using twoor more types of "living" sites in the core, with differently reactiblefunctional groups on the arms, more than two different types of arms canresult.

The multifunctional linking agent referred to above can be any moleculehaving at least two plymerizable carbon-carbon double bonds. Examples ofsuitable linking agents are:

ethylene dimethacrylate

1,3-butylene dimethacrylate

tetraethylene glycol dimethacrylate

triethylene glycol dimethacrylate

trimethylolpropane trimethacrylate

1,6-hexylene dimethacrylate

1,4-butylene dimethacrylate

ethylene diacrylate

1,3-butylene diacrlate

tetraethylene glycol diacrylate

triethylene glycol diacrylate

trimethylolpropane triacrylate

1,6-hexylene diacrylate

1,4-butylene diacrylate

other useful ingredients and techniques will be found in the hereinincorporated above-mentioned U.S. Patents, especially U.S. Pat. No.4,417,034--Webster, in columns 1-9.

INTRODUCTION TO EXAMPLES

The ingredients and procedures used in the examples are outlined belowto aid in understanding the invention.

I. Starting Materials A. Initiators Isobutyl Initiator

1-trimethylsiloxy-1-isobutoxy-2-methylpropene ##STR16##

Molecular Weight: 216.39

OH-Blocked Initiator

1-(2-trimethylsiloxyethoxy)-1-trimethylsiloxy-2-methylpropene ##STR17##

Molecular weight: 276.52

B. Catalysts TASHF₂

Tris(dimethylamino)sulfonium bifluoride ##STR18##

TBAHF₂

Tetrabutylammonium bifluoride

(C₄ H₉)₄ N.sub.⊕ HF₂.sup.⊖

TBACF

Tetrabuytlammonium chlorobenzoate

C. Solvents Glyme

1,2-dimethoxyethane

CH₃ OCH₂ CH₂ OCH₃

Others

Acetonitrile=CH₃ CN

Xylene

THF=Tetrahydrofuran= ##STR19##

D. Monomers MMA

methy methacrylate ##STR20##

M.W.=100.12

2EHMA

2-ethylhexyl methacrylate ##STR21##

M.W.=198.29

IEM

2-isocyanatoethyl methacrylate ##STR22##

M.W.=155.14

AMA

allyl methacrylate ##STR23##

M.W.=126.14

EGDMA

ethylene glycol dimethacrylate ##STR24##

M.W.=198.20

TEGDMA

tetraethylene glycol dimethacrylate ##STR25##

M.W.=330.34

II. Reactions A. Polymerization of MMA with "Isobutyl Initiator"##STR26## B. Polymerization of MMA with "OH-Blocked Initiator" ##STR27##C. Preparation of Star Polymers

Let "IS" represent the initiator, where "I" is the part that remains atthe beginning of the polymer chain (i.e., ##STR28## and where "S"represents the part of the initiator that goes to the other ("living")end of the polymer chain and is eventually removed by reaction withmethanol.

Let "M" represent a mono-methacrylate (e.g., MMA).

Let ##STR29## represent a dimethacrylate (e.g., (EGDMA) 1. Preparationby "Arm First" Method

    ______________________________________                                        a.     Polymerize "M"                                                                 ##STR30##                                                             b.     Add "M M"                                                                      ##STR31##                                                                     ##STR32##                                                             c.     Add Methanol to Remove "S"                                                    Final polymer is:                                                              ##STR33##                                                             ______________________________________                                    

This star has 3 arms, each arm having been made from 5 monomermolecules.

Calculation ##EQU1## where (IS)=moles of initiator

(M-M)=moles of dimethacrylate

in above example, ##EQU2##

2. Preparation by "Core First" Method ##STR34##

This star has 3 arms, each arm having been made from 5 monomermolecules.

3. Comparison of "Arm First" and "Core First" Method

a. Calculation are the same.

b. Structures are similar except for point of attachment of initiatorfragment "I".

(1) in "arm first" method, "I" becomes attached to outside ends of arms.

(2) in "core first" method, "I" becomes attached to core.

Thus, since "I" can be made to carry a functional group (e.g., an OHgroup when the OH-blocked initiator is used), it is possible to makestars having functional groups attached to the outside ends of the arms(by the "arm first" method) or attached to the core (by the "core first"method).

4. Preparation of Giant Stars

Note that the size of the arms can be varied by changing the ratio(M)/(IS) (where (M)=moles of mono-methacrylate and (IS)=moles ofinitiator). Long arms are obtained when (M)/(IS) is large.

Note also that the number of arms can be varied by changing the ratio(IS)/(M-M) (where (IS)=moles of initiator and (M-M)=moles ofdimethacrylate). A large number of arms results when (IS)/(M-M) is madeclose to, but greater than 1.00.

Thus, if 1.05 moles of initiator are used with 1.00 moles ofdimethacrylate, the resulting star will have 21 arms. ##EQU3##

If the ratio (IS)/(M-M) is equal to or less than 1.00, as in a preferredembodiment of the invention, the equation fails and the number of armscannot be calculated. In this case, (e.g., when (IS)/(M-M)=0.25) acrosslinked core is obtained having a very large number of arms (e.g.,200). Most of the examples show the preparation of these gaint stars.

If a more lightly crosslinked core is desired, monfunctional acrylic canbe substituted for difunctional or higher functionality acrylics. Theamount of substitution can range from a small but effective amount forfor the purpose of decreasing the crosslink density up to 99% by weightmonofunctional ingredients,measured on the basis of total acrylics. Suchsmall amounts can be less than 1%, event as little as 0.1 or 0.01%, byweight. Because of the flexibility in designing systems with from muchto little crosslinking in the core, when the claims say "crosslinked",they mean more or less crosslinked, depending on the proportion ofmonofunctional and multifunctional acrylics in the core.

In the examples and elsewhere, parts, percentages and proportions aregiven by weight except where indicated otherwise.

EXAMPLE 1

This describes the preparation of a poly(methyl methacrylate) starpolymer by making the arms polymer first and then connecting the armtogether.

The polymer is useful as a rheology control agent in high solids paintsof both the unicoat and color coat/clear coat types.

A three-neck round bottom flask fitted with a mechanical stirrer, areflux condenser, a rubber septum, a temperature probe and provision formaintaining a dry nitrogen atmosphere was used as a. reaction vessel.After purging with dry nitrogen, the flask was charged with thefollowing initial charge:

Initial Charge

1189.0 g glyme

15.54 g xylene

14.0 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initail catalyst:

Initial Catalyst

100 microliters of a 1.0 molar solution of tetrabutylammonium bifluoride(TBAHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. At the beginning of the first feed, a clock wasstarted and left running to keep track of the feeds and other steps. Thefeed compositions and the clock times (in minutes) at which theadditions of the feed compositions were started and completed were asfollows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     300 microliters,  0         90                                                1.0 M TBAHF.sub.2 and                                                         5.3 g glyme                                                             II    844.4 g methyl methacrylate                                                                     0         40                                          III   55.8 g ethylene glycol                                                                          55        70                                                dimethacrylate                                                          ______________________________________                                    

During the additions of the feeds, the temperature gradually rose,reaching a maximum of 86° C. at a clock time of 30 minutes.

At a clock time of 55 minutes, before the addition of Feed III wasstarted, a 50 g portion of the reaction mixture (Sample 1) was removedfor testing and quenched by the addition of 2 ml methanol.

At a clock time of 100 minutes, the reaction mixture was quenched by theaddition of quencher:

Quencher

20 g methanol

The resulting clear solution of star polymer had a solids content of43.1% (vs 42.45% theoretical).

The arm polymer was present in Sample 1 at a solids content of 37.8% (vs40.50% theoretical) indicating that about 94% of the methyl methacrylatehad polymerized at the time the sample was taken. Analysis by gelpermeation chromatography (GPC) showed a number average molecular weightof 11,900 (vs 13,00 theoretical), a weight of average molecular weightof 18,100 and a dispersity 1.52 for the arm polymer

Light scattering and viscosity measurements on similar star polymersshow molecular weights of about 2.7 million. Thus, the star polymer hason the order of 200 arms, each having a molecular weigh of about 12,000.

EXAMPLE 2

This describes the preparation of a poly(methyl methacrylate) starpolymer having arms terminated with hydroxyl groups.

The polymer can be used as a rheology control agent and is especiallyuseful in enamels, where the hydroxyl groups allow the star polymermolecules to become a part of the polymer network making up thecrosslinked enamel film. The polymer can also be used as an enamelbinder polymer by combining it with a polyisocyanate or amelamine/formaldehyde resin. The polymer can also be used as a precursorfor further reactions (e.g., the introduction of methacrylatefunctionality as described in Example 3).

The reaction vessel described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

800.24 g glyme

4.8 g xylene 8.34 g 1- (2-trimethylsiloxyethoxy)-1-trimethylsiloxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of TBAHF₂ in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     300 microliters of                                                                              0         80                                                1 M TBAHF.sub.2 and                                                           3.0 g glyme                                                             II    310.18 g methyl   0         30                                                methacrylate                                                            III   39.62 g tetraethyleneglycol                                                                     45        60                                                dimethacrylate                                                          ______________________________________                                    

During the additions of the feeds, the temperature gradually rose,reaching a maximum of 62° C. at 40 minutes.

At a clock time of 45 minutes, before the addition of Feed III wasstarted, a 2 g portion of the reaction mixture was (Sample 1) removedfor testing and quenched.

At 110 minutes, the reaction was quenched and the hydroxyl groupsunblocked by the addition of quencher:

Quencher

30.0 g methanol

3.0 g of a 1 molar solution of a tetrabutylammonium floride intetrahydrofuran

The resulting star polymer was isolated by precipitation in methanol anddried in a vacuum oven. As in Example 1, the star has a large number ofarms, but in this case, the arms have a molecular weight of about 10,000and each arm is terminated by a hydroxyl group. The star polymer hasabout 0.0852 milliequilvalents OH per gram of solids (or a hydroxylnumber of about 4.78 mg KOH/g polymer).

EXAMPLE 3

This describes the preparation of a star polymer having terminalmethacrylate groups by reaction of the star polymer of Example 2 with2-isocyanatoethyl methacrylate.

The polymer is useful as a toughening modifier for plastics such as castpoly(methyl methacrylate) sheet, pigmented, filled such as with hydratedaluminum oxide, or clear. It may also be used in coatings and inphotopolymerizable systems.

The dry star polymer of Example 2 (150.00 g, 0.0128 equivalents OH) wasdissolved in 300.02 g dry glyme. Then 2.29 g (0.0148 mole )2-isocyanatoethyl methacrylate and 2 drops of a 10% solution ofdibutyltin dilaurate inmethyl ethyl ketone was added and the mixturestirred. After standing over the weekend, the reaction mixture was foundto have lost its IR band at 2356 cm⁻¹ (NCO) showing that the reactionwas substantially complete.

The resulting star polymer has a large number of poly(methylmethacrylate) arms, each having a molecular weight of about 10,000 andeach terminated with a methacrylate group.

EXAMPLE 4

This describes the preparation of a star polymer in which the arms are ablock copolymer of methyl methacrylate and 2-ethylhexyl methacrylate.The polymer is prepared by making the core first and then polymerizingthe arms onto it.

The polyme can be used as a rheology control agent or toughening agentin coatings or plastics.

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

88.14 g glyme

1.16 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tris(dimethylamino) sulfoniumbifluoride in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     200 microliters of 1.0 M                                                                         0        80                                                TASHF.sub.2 and 2.0 g                                                         acetonitrile                                                            II    1.02 g ethylene glycol                                                                           0        10                                                dimethacrylate                                                          III   29.57 methyl methacrylate                                                                       20        35                                          IV    27.73 g 2-ethylhexyl                                                                            45        60                                                methacrylate                                                            ______________________________________                                    

During the additions of the feeds, the temperature gradually rose,reaching a maximum of 48° C. at 45 minutes.

At a clock time of 90 minutes, the reaction was quenched by the additionof quencher:

Quencher

2.0 g methanol

The resulting star polymer has a core to which is attached veryapproximately 25 arms. Each arm has a molecular weight of about 10,700and consists of two blocks: a poly(methyl methacrylate block of about5500 molecular weight attached at one end to the core and apoly(2-ethyl-hexyl methacrylate) block of about 5200 molecular weightattached at one end to the other end of the poly(methyl methacrylate)block.

EXAMPLE 5

This describes the preparation of a star polymer having both poly(methylmethacrylate) arms and poly(2-ehtylhexylmethacrylate) arms on the samestar polymer molecule.

The polymer can be used as a rheology control agent or toughening agentin coatings or plastics.

The poly(methyl methacrylate) arm polymer (a) and the poly(2-ethylhexylmethacrylate) arm polymer (b) were prepared simultaneously in separatereaction flasks and, without quenching, were mixed together beforepreparing the star polymer (c).

A. POLY(METHYL METHACRYLATE) ARM POLYMER

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

50.26 g glyme

0.65 g xylene

0.55 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tris(dimethylamino)-sulfoniumbifluoride (TASHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     50 microliters of 1 M TASHF.sub.2                                                                0        30                                                and 1.0 g acetonitrile                                                  II    30.42 g methyl methacrylate                                                                      0        20                                          ______________________________________                                    

At a clock time of 30 minutes a 1 portion (Sample A-1) of the reactionmixture was removed and quenched in methanol.

B. POLY(2-ETHYLHEXYL METHACRYLATE) ARM POLYMER

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

44.13 g glyme

0.52 g xylene 1.16 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

Initial Catalyst

50 microliters of a1.0 molar solution of tris(dimethylamino) sulfoniumbifluoride (TASHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition Addition                                     Feed    Feed Composition                                                                              Started  Completed                                    ______________________________________                                        I       100 microliters of                                                                            0        30                                                   1 M TASHF.sub.2                                                               and 1.0 g acetonitrile                                                II      28.82 g 2-ethylhexyl                                                                          0        20                                                   methacrylate                                                          ______________________________________                                    

At a clock time of 30 minutes, a 1 g portion of the resulting solutionwas then removed and quenched in methanol (Sample B-1).

C. STAR POLYMER

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with a mixture of the arm polymer solutions describedin A and B. The initial charge is:

Initial Charge

81.97 g arm polymer solution A

69.61 g arm polymer solution B

The initial charge was then stirred continuously under dry nitrogenwhile adding the feed compositions shown below at constant rates viasyringe pumps. The feed compositions and the addition schedule were asfollows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     50 microliters of 1 M TASHF.sub.2                                                                30       60                                                and 1.0 g acetonitrile                                                  II    4.86 g ethylene glycol                                                                           30       40                                                dimethacrylate                                                          ______________________________________                                    

At a clock time of 70 minutes, the reaction was quenched by the additionof quencher:

Quencher

2.0 g methanol.

A portion of the resulting star polymer solution (Sample C-1) wasremoved for testing.

Analysis of the sample by HPLC showed the following:

    ______________________________________                                        Sample  Identification  Conversion of Monomer                                 ______________________________________                                        A-1     MMA arm polymer 69.3%                                                 B-1     2EHMA arm polymer                                                                             98.4%                                                 C-1     Star Polymer    99.75%   (MMA)                                                                99.47%   (2EHMA)                                                              98.9%    (EGDMA)                                      ______________________________________                                    

The resulting star polymer had the following composition by weight.

8% Core

49% MMA arms (Mn=12,000)

43% 2EHMA arms (Mn=5,500)

EXAMPLE 6

This describes the preparation of a star polymer having both poly(methylmethacrylate) arms and poly(2-ethylhexyl methacrylate) arms on the samestar polymer molecule. In this case, the poly(methyl methacrylate) arempolymer is made first, then a star polymer is made from it, and finallypoly(2-ethylhexyl methacrylate) arms are grown from the star polymer.

The polymer can be used as a rheology control agent or toughening agentin coating or plastics.

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

176.29 g glyme

2.09 g xylene

1.24 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1 molar solution of tetrabutylammonium bifluroide inglyme. The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     200 microliters 1 M TBAHF.sub.2.sup.2                                                             0       90                                                and 2.0 g glyme                                                         II    62.22 g methyl methacrylate                                                                       0       15                                          III   4.31 g ethylene glycol                                                                           30       40                                                dimethacrylate                                                          IV    57.88 g 2-ethylhexyl                                                                             50       65                                                methacrylate                                                            ______________________________________                                    

During the additions, the temperature gradually increased, reaching amaximum of 55° C. at 15 minutes.

At a clock time of 48 minutes a 1.5 g portion of the mixture (Sample 1)was removed and quenched in methanol.

At a clock time of 100 minutes, the reaction was quenched by theaddition of quencher:

Quencher

2.0 g methanol

The resulting solution of star polymer had a solids content of 28.3%(vs. 40.72%) suggesting a conversion of about 70%. The star polymer hasan approximate composition of

3.5% Core

49.9% MMA arms (Mn=11,000)

46.7% 2EHMA arms (Mn=10,000)

EXAMPLE 7

This describes the preparation of a poly(methyl methacrylate) starpolymer having allyl functionality at the ends of the arms. In thiscase, the core is prepared first.

The polymer is useful as an additive for plastic sheeting, air-dryfinishes, low bake finishes and poly(methyl methacrylate) sheet.

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

89.5 g glyme

1.07 g xylene

1.23 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1 molar solution of tris(dimethylamino)-sulfoniumbifluoride (TASHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     4.47 g ethylene glycol                                                                            0        5                                                dimethacrylate                                                          II    200 microliters 1.0 M TASHF.sub.2                                                                 0       60                                                and 2.0 g acetonitrile                                                  III   61.06 g methyl methacrylate                                                                      15       45                                          IV    0.84 g allyl methacrylate                                                                        55       Instant                                           (AMA)                                                                   ______________________________________                                    

During the additions, the temperature rose, reaching a maximum of 58° C.at 45 minutes.

At a clock time of 45 minutes a 1 g portion of the reaction mixture wasremoved (Sample 1) and quenched in methanol.

At a clock time of 70 minutes, the polymer was quenched by the additionof quencher:

Quencher

2.0 g methanol

A portion of the resulting star polymer solution was removed for testing(Sample 2).

Analysis by high pressure liquid chromatograph (HPLC) of Samples 1 and 2gave the following conversions of monomers

    ______________________________________                                                         % Conversion                                                 ______________________________________                                        Sample 1           94.4 (MMA)                                                                    96.5 (EGDMA)                                               Sample 2           93.5 (MMA)                                                                    28.3 (AMA)                                                 ______________________________________                                    

The star polymer thus prepared has the following approximatecomposition.

7% Core

93% MMA/AMA arms (Mn=11,000)

EXAMPLE 8

This describes the preparation of a poly(methyl methacrylate) starpolymer having butylacrylate blocks at the ends of the arms. In thiscase, the core is prepared first.

The polymer is useful as an additive for plastic sheeting, air-dryfinishes, low bake finishes and poly(methyl methacrylate) sheet.

A reaction vessel as described in Example 1 was purged with dry nitrogenand then charged with the following initial charge:

Initial Charge

699.6 g THF

5.0 g xylene

7.0 g 1-trimethylsiloxy-1-methoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1 molar solution of tris(dimethylamino)-sulfoniumbifluroide (TASHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     40.7 g hexane diol  0       10                                                dimethacrylate                                                          II    400 microliters 1.0 M TBACB                                                                       0       90                                                and 4.1 g THF                                                           III   199.5 g methyl methacrylate                                                                      40       55                                          IV    255.8 g butylacrylate                                                                            85       Instantly                                   ______________________________________                                    

During the additions, the temperature rose, reaching a maximum of 58° C.at 45 minutes.

At a clock time of 45 minutes a 1 g portion of the reaction mixture wasremoved (Sample 1) and quenched in methanol.

At a clock time of 120 minutes, the polymer was quenched by the additionof 10.0 g methanol.

EXAMPLE 9

This describes the preparation of a poly(2-ethylhexyl methacrylate) starpolymer.

The polymer has a low glass transition temperature and is especiallyuseful as an additive for improving the impact resistance of plastics orthe toughness of coatings.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

112.55 g glyme

1.4 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tris(dimethylamino)-sulfoniumbifluoride in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     200 microliters in TASHF.sub.2                                                                  0         60                                                and 2.0 g acetonitrile                                                  II    4.85 g ethylene glycol                                                                          0          5                                                dimethacrylate                                                          III   58.47 g 2-ethylhexyl                                                                            15        45                                                methacrylate                                                            ______________________________________                                    

During the additions, the temperature rose, reaching a maximum of 41° C.at 50 minutes.

At a clock time of 70 minutes, the polymer was quenched by the additionof quencher.

Quencher

2.0 g methanol

The resulting solution of star polymer contains 36.7% solids (vs 35.44%theoretical). The star polymer consists of about 8% core and about 92%arm, the arms being poly(2-ethylhexyl methacrylate) having a numberaverage molecular weight of about 9000.

EXAMPLE 10, DISPERSION OF A LARGE CORE STAR

This describes the preparation of a dispersion of a star polymer byconducting the polymerization in hexane. The relatively large core is acopolymer of methyl methacrylate and ethylene glycol dimethacrylate.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

72.0 g hexane

17.4 g tetrahydrofuran

1.27 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     200 microliters of                                                                               0        80                                                1 M TBAHF.sub.2                                                         II    23.1 g 2-ethylhexyl                                                                              0        15                                                methacrylate                                                            III   14.15 g methyl methacrylate                                                                     30        40                                          IV    24.0 g methyl methacrylate                                                                      50        65                                                and 4.42 g ethylene glycol                                                    dimethacrylate                                                          ______________________________________                                    

At 90 minutes, the reaction was quenched by the addition of quencher:

Quencher

2.0 g methanol

The resulting composition was a dispersion in hexane of a star polymerconsisting of a core to which many arms are attached. The core accountsfor 43% by weight of the star polymer and is a crosslinked copolymer of16% by weight ethylene glycol dimethacrylate and 84% methylmethacrylate. The arms account for 57% by weight of the copolymer. Eacharm is a block copolymer consisting of 1 block of poly(2-ethylhexylmethacrylate) having a number average molecular weight of about 4080 and1 block of poly(methyl methacrylate) having a number average molecularweight of about 2410. The poly(methyl methacrylate) block has one endattached to the core. The poly(2-ethylhexyl methacrylate) block is freeat one end and has the other end attached to the outboard end of thepoly(methyl methacrylate) block.

EXAMPLE 11, DISPERSION OF A SMALL CORE STAR

This describes the preparation of a dispersion of a star polymer byconducting the polymerization in hexane. In this case, the core issmaller than that obtained in Example 10.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

72.3 g hexane

18.2 g tetrahydrofuran

1.24 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     200 microliters of 1 M                                                                           0        90                                                TBAHF.sub.2 and 2.24 g                                                        tetrahydrofuran                                                         II    30.7 g 2-ethylhexyl                                                                              0        15                                                methacrylate                                                            III   32.4 g methyl methacrylate                                                                      30        45                                          IV    4.1 g ethylene glycol                                                                           55        70                                                dimethacrylate                                                          ______________________________________                                    

At 100 minutes, the reaction was quenched 15 by the addition ofquencher:

Quencher

2.0 g methanol

The resulting composition was a dispersion in hexane of a star polymerconsisting of a core to which many arms are attached. The core, whichwas made from ethylene glycol dimethacrylate, accounted for 6.1% byweight of the star polymer. The arms accounted for 93.9% by weight ofthe star polymers. Each arm was a block copolymer consisting of 1 blockof poly(2-ethylhexyl methacrylate) having a number average molecularweight of about 5500 and 1 block of poly(methyl methacrylate) having anumber average molecular weight of about 5650. The poly(methylmethacrylate) block has one end attached to the core. Thepoly(2-ethylhexyl methacrylate) block is free at one end and has theother end attached to the outboard end of the poly(methyl methacrylate)block.

COMPARATIVE TEST A, GELLED GTP BATCH

This example shows that a simultaneous addition (as opposed tosequential addition in the other examples) of monomethacrylate anddimethacrylate produced a gel rather than the desired star polymer.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

88.74 g glyme

1.25 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the intended additionschedules were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     100 microliters of 1 M                                                                          0         45                                                TBASF.sub.2 in 2.0 g glyme                                              II    60.0 g methyl methacrylate                                                                      0         30                                                and 4.6 g ethylene glycol                                                     dimethacrylate                                                          ______________________________________                                    

At a clock time of about 15 minutes, the reaction solution gelled. Atthe time of gellation, the mole ratio of the components which had beenadded was 1:2:52 of initiator: dimethacrylate: monomethacrylate.

COMPARATIVE TEST B, FREE RADICAL CONTROL

This shows that a mixture of monomethacrylate and dimethacrylate gelswhen polymerized by a free radical process.

A reaction vessel was charged with the following initial charge:

Initial Charge

25.0 g toluene

The initial charge was heated to reflux and then held at reflux andstirred continuously while adding the feed composition shown below atconstant rate via a syringe pump. The feed composition and additionschedule were as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     25.0 g methyl methacrylate                                                    1.4 g ethylene glycol                                                         dimethacrylate                                                                0.25 g Vazo ® 67                                                                            0         60                                          ______________________________________                                    

At a clock time of about 30 minutes, the reaction solution gelled. Atthe time of gellation, the mole ratio of the added reactants was1:5.4:192 of initiator: dimethacrylate: monomethacrylate.

EXAMPLE 12, LIGHTLY CROSSLINKED CORE

This describes the preparation of a star polymer having a core which isnot as highly crosslinked as those in other examples. The core is madefirst in this example.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

86.4 g glyme

1.21 l g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1 molar solution of tetrabutylammonium bifluoride(TBAHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     200 microliters 1 M IBAHF.sub.2                                                                  0        80                                                and 2.0 g glyme                                                         II    4.09 g ethylene glycol                                                                           0        15                                                dimethacrylate and                                                            2.54 g methyl methacrylate                                              III   58.93 g methyl methacrylate                                                                      30       60                                          ______________________________________                                    

At 90 minutes, the reaction was quenched 30 by the addition of quencher:

Quencher

2.0 g methanol

The resulting star polymer consists of about 11% by weight core andabout 89% by weight arms. The core, having been made from a ratio ofabout 62% by weight ethylene glycol dimethacrylate and about 38% byweight methyl methacrylate is not as highly crosslinked as cores madefrom ethylene glycol dimethacrylate alone.

EXAMPLE 13, LIGHTLY CROSSLINKED CORE, ARM FIRST

This describes the preparation of a star polymer having a core which isnot as highly crosslinked as those in other examples. In this case, thearm polymer is made first.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

91.07 g glyme

1.2 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoride(TBAHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     200 microliters 1.0 M                                                                            0        80                                                TBAHF.sub.2 and 2.0 g glyme                                             II    63.98 g methyl methacrylate                                                                      0        30                                          III   4.4 g ethylene glycol                                                                            45       60                                                dimethacrylate and 6.6 g                                                      methyl methacrylate                                                     ______________________________________                                    

At 90 minutes, the reaction was quenched by the addition of quencher:

Quencher

2.0 g methanol

The resulting star polymer consisted of about 85.5% by weight of armpolymer and about 14.5% by weight of core. The core, having been madefrom a 40:60 weight ratio of dimethacrylate to monomethacrylate was notas tightly crosslinked as cores made from ethylene glycol dimethacrylatealone. The arms consisted of polymethyl methacrylate having a numberaverage molecular weight of about 11,700.

EXAMPLE 14, STAR POLYMER HAVING TWO KINDS OF ARMS WITH AND WITHOUT GMA

This describes the preparation of a star polymer having two kinds ofarms. One kind of arm is polymethyl methacrylate; the other kind ispolymethyl methacrylate capped with a block of polyglycidylmethacrylate.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

187.7 g glyme

5.2 g xylene

1.4 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

100 microliters of a 1.0 molar solution of tetrabutylammonium bilfuoride(TBAHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen at 0° C. while adding the feed compositions shown below atconstant rates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     400 microliters of 1.0 M                                                                          0       100                                               TBAHF.sub.2 and 6.17 glyme                                              II    39.89 g methyl methacrylate                                                                       0       10                                          III   6.92 g ethylene glycol                                                                           20       35                                                dimethacrylate                                                          IV    78.58 g methyl methacrylate                                                                      50       70                                          V     3.9 g glycidyl     83       83                                                methacrylate                                                            ______________________________________                                         (Feed V was added in one shot at a clock time of 83 minutes. At a clock       time of 115 minutes, the reaction was quenched by the addition of             quencher)                                                                

Quencher

3.0 g methanol

The resulting star polymer consists of about 5.3% by weight of core towhich were attached about 31.3% by weight of polymethyl methacrylatearms and about 53.4% by weight of block copolymer arms. The polymethylmethacrylate arms had a number average molecular weight of about 6300.The block copolymer arms had a number average molecular weight of about12,700 and consists of a polymethyl methacrylate block having a numberaverage molecular weight of about 12,100 and a polyglycidyl methacrylateblock having a number average molecular weight of about 600. Thepolymethyl methacrylate block of each block copolymer arm was attachedto the core and the polyglycidyl methacrylate block (which consisted ofabout 4 monomer units of glycidyl methacrylate) was attached to theoutboard end of the polymethyl methacrylate block. On a number basis,50% of the arms had no glycidyl group and the other 50% of the arms had4 glycidyl groups each at their outer ends.

EXAMPLE 15, STAR POLYMER WITH 2 KINDS OF ARMS

This describes the preparation of a star polymer with two differentkinds of arms.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

183.3 g glyme

1.96 g xylene

1.31 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoride(TBAHF₂) in glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and the additionschedules were as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters 1.0 M                                                                             0       90                                                TBAH.sub.2 and 4.58 g glyme                                             II    27.77 g 2-ethylhexyl                                                                              0       10                                                methacrylate                                                            III   5.32 g ethylene glycol                                                                           25       40                                                dimethacrylate                                                          IV    88.54 g methyl methacrylate                                                                      50       70                                          ______________________________________                                    

At a clock time of 100 minutes, the reaction mixture was quenched by theaddition of quencher:

Quencher

2.0 g methanol

The resulting star polymer consisted of a core to which many arms wereattached. The composition was:

4.3% core of EGDMA

23.4% ZEHMA arm (Mn=4,700)

72.3% MMA arm (Mn=14,600)

EXAMPLE 16

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

179.37 g glyme

4.85 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

2.4 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microlieters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters of 1.0 M                                                                         0        80                                                TBAHF.sub.2 and 3.0 g glyme                                             II    133.04 g methyl methacrylate                                                                     0        30                                          III   13.55 g ethylene   45       60                                                dimethacrylate                                                          ______________________________________                                    

At a clock time of 45 minutes, a 101.28 g sample was removed foranalysis and quenched by the addition of 2.0 g methanol.

At a clock time of 95 minutes, 2 g methanol was added.

EXAMPLE 17

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

178.32 g glyme

2.34 g 1-trimethylsiloxy-isobutoxy-2-methylpropene

1.72 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters of 1.0 M                                                                         0        80                                                TBAHF.sub.2 and 3.0 g glyme                                             II    128.39 g methyl methacrylate                                                                     0        30                                          III   6.85 g ethylene    45       60                                                dimethacrylate                                                          ______________________________________                                    

At a clock time of 45 minutes, a 94.09 g sample was removed for analysisand quenched by the addition of 2.0 g methanol.

At a clock time of 95 minutes, 2 g methanol was added.

An additional advantage of making star polymers by group transferpolymerization is that it gives good molecular weight control of boththe arm and the star. That is, narrow molecular weight dispersities areobtained when these components are measured by Gel PermeationChromatography. For example, the process of this Example 16 wouldtypically give arms that would have a MN=11,900; MW=18,000; and D(MW/MN)=1.51 when measured by GPC. The star made from these arms wouldhave a MN=312,000; MW=455,000; and D=1.46. This is in contrast toprevious attempts to make methacrylate stars. Zilliox (J. Zillox. P.Rempp, and J. Parrod, J. Polymer Science: Part C, Polymer Symposia No.22, pp 145-156 (1968)) reported that the methacrylate star he made byanionic polymerization is polydispersed because the number of branches(attached arms) fluctuates appreciably.

EXAMPLE 18

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

181.43 g glyme

4.55 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

2.23 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed Feed Composition    Started  Completed                                   ______________________________________                                        I    300 microliters of   0       80                                               1.0 M TBAHF.sub.2 and                                                         3.0 g glyme                                                              II   13.99 g ethylene dimethacrylate                                                                   30       60                                          III  83.63 g methyl methacrylate                                                                       61       71                                          ______________________________________                                    

At a clock time of 130 minutes, 2 g methanol was added to quench theliving polymer.

EXAMPLE 19

This describes a preferred procedure for the polymerization of methylmethacrylate using an oxyanion catalyst and acetonitrile as a solventand a catalyst longevity enhancer.

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

110.0 g THF

1.0 g 1-trimethylsiloxy-1-methoxy-2-methylpropene

1.0 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammoniumm-chloroacetate in acetonitrile.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                          Clock Time (Minutes)                                                                Addition  Addition                                    Feed  Feed Composition  Started   Completed                                   ______________________________________                                        I     50 microliters of 0         80                                                1.0 M TBACB and                                                               3.0 g acetonitrile                                                      II    62.9 g methyl methacrylate                                                                      0         30                                          III   7.0 g ethylene    61        71                                                dimethacrylate                                                          ______________________________________                                    

At a clock time of 30 minutes, a 34.20 g sample was removed for analysisand quenched by the addition of 2.0 g methanol.

At a clock time of 130 minutes, 2 g methanol was added to quench theliving polymer.

EXAMPLE 20

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

178.33 g glyme

2.48 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

2.00 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters of 0        80                                                1.0 M TBAHF.sub.2 and                                                         3.0 g glyme                                                             II    8.77 g ethylene    0        15                                                dimethacrylate                                                          III   83.92 g methyl methacrylate                                                                      30       60                                          ______________________________________                                    

At a clock time of 30 minutes, a 30.04 g sample was removed for analysisand quenched by the addition of 2.0 g methanol.

At a clock time of 100 minutes, 2 g methanol was added.

EXAMPLE 21

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

b 184.46 g glyme

1.14 g 1-trimethylsiloxy-1-isobutoxy-2-methylpropene

2.31 g xylene

To the initial charge was then added via syringe the initial catalyst:

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuouly under drynitrogen while adding the feed compositions shown below at constantrates via syringe pumps. The feed compositions and addition scheduleswere as follows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters of 0        80                                                1.0 M TBAHF.sub.2 and                                                         3.0 g glyme                                                             II    5.85 g ethylene    0        15                                                dimethacrylate                                                          III   87.24 g methyl methacrylate                                                                      30       60                                          ______________________________________                                    

At a clock time of 30 minutes, a 44.90 g sample was removed for analysisand quenched by the addition of 2.0 methanol.

At a clock time of 100 minutes, 2 g methanol was added.

EXAMPLE 22

A reaction vessel as described in Example 1 was purged with nitrogen andthen charged with the following initial charge:

Initial Charge

182.0 g glyme

1.32 g 1-trimethylsiloxy-1-isobutyoxy-2-methylpropene

2.02 g xylene

To the initial charge was then add via syringe the inital catalyst.

Initial Catalyst

50 microliters of a 1.0 molar solution of tetrabutylammonium bifluoridein glyme.

The mixture thus obtained was then stirred continuously under drynitrogen while adding the feed composition shown below at constant ratesvia syringe pumps. The feed compositions and addition schedules were asfollows:

    ______________________________________                                                           Clock Time (Minutes)                                                                Addition Addition                                    Feed  Feed Composition   Started  Completed                                   ______________________________________                                        I     300 microliters of 1.0 M                                                                         0        80                                                TBAHF.sub.2 and 3.0 g glyme                                             II    119.1 g methyl methacrylate                                                                      0        30                                          III   3.15 g ethylene    45       60                                                dimethacrylate                                                          ______________________________________                                    

At a clock time of 45 minutes, a 75.0 g sample was removed for analysisand quenched by the addition of 2.0 g methanol.

At a clock time of 95 minutes, 2 g methanol was added.

ANALYTICAL CHARACTERIZATION OF STAR POLYMERS EXAMPLES 12-13, 16-18 AND20-22

Some of the star polymers described above were characterized byquasielastic laser light scattering (QUELS) and by intrinsic viscosity.The "QELS" technique is described by F. B. Malihi, T. Provder and M. E.Kohler, Journal of Coatings Technology, vol. 55, No. 702, pp. 41-48(July, 1983) and B. J. Berne and R. Pecora, "Dynamic Light Scattering",John Wiley & Sons, New York (1976), measurement of intrinsic viscosity"is described by J. F. Rabek, "Experimental Methods in PolymerChemistry", John Wiley & Sons, New York (1980), pp 125-128 and by W. R.Sorenson and T. W. Campbell, "Preparative Methods of Polymer Chemistry",Second Edition, Interscience Publishers, New York (1968), pp 44-50.

The molecular weights of the star polymers were calculated from thehydrodynamic radius, R_(H), obtained by the "QELS" technique and fromthe intrinsic viscosity, [η], according to the following equation:##EQU4## where M=molecular weight of the star polymer

N₁ =Avogadro's constant=6.023×10²³ mol⁻¹

R_(H) =hydrodynamic radius from "QELS"

[η]=intrinsic viscosity

All measurements were made in methyl ethyl ketone.

The number of arms for star polymer molecule was calculated by dividingthe molecular weight of the star polymer by the weight average molecularweight (as determined by GPC) of the arm polymer. Although thiscalculation is strictly valid only when the star molecule is in solutionand the hydrodynamic diameter is less than 600 angstroms, thecalculations were also done for the larger stars for comparison.

The results are shown below in Table I.

                  TABLE 1                                                         ______________________________________                                        Star                    Molecular                                             Polymer Intrinsic                                                                              Weight --M.sub.w                                                                             Number of                                     of     Viscosity D.sub.H                                                                              of      of     Arms per                               Example                                                                              (ml/g)    (Å)                                                                              Stars   Arms   Star                                   ______________________________________                                        12     19.68     1214   7.17 × 10.sup.7                                                                 16,600 4320                                   13     14.72      227   6.26 × 10.sup.5                                                                 16,600  38                                    16     23.87     1000   3.31 × 10.sup.7                                                                  8,035 4120                                   17     14.89      387   3.07 × 10.sup.6                                                                 16,600  185                                   18     11.37     4380   5.83 × 10.sup.9                                                                  8,035 7.26 × 10.sup.5                  20     20.37     3600   1.81 × 10.sup.9                                                                 16,600 1.09 × 10.sup.5                  21     21.44     2900   1.55 × 10.sup.9                                                                 27,900 5.56 × 10.sup.4                  22     20.91      155   4.29 × 10.sup.5                                                                 27,900  15                                    ______________________________________                                    

These results show that this invention provides acrylic star polymersthat can be designed to have any of a wide range of molecular sizes,lengths of arms and numbers of arms per molecule.

EXAMPLE 23

The following example shows the use of star polymers in coatings.

The following compositions are prepared and then blended together toform a high solids white enamel.

    ______________________________________                                        Acrylic Polymer Solution 80.0                                                 (a polymer of styrene/methyl                                                  methacrylate/butyl acrylate/hydroxyethyl                                      acrylate 15/15/40/30 prepared at 75%                                          solids in methyl amyl ketone using                                            conventional free radical techniques)                                         Star Polymer (described in Example 18)                                                                 25.0                                                 White Millbase                                                                (a standard millbase composed of 70%                                          white pigment, 10% acrylic polymer [from                                      acrylic polymer solution described                                            above], and 20% methyl amyl ketone                                            Melamine Resin           30.0                                                 P-toluene Sulfonic Acid Solution                                                                       2.8                                                  (17.7% P-toluene sulfonic acid, 12.5%                                         dimethyl oxazolidine, and 69.8%                                               methanol)                                                                     Xylene                   40.0                                                 Methyl Amyl Ketone       22.2                                                 Total                    200.0                                                ______________________________________                                    

The above composition was sprayed onto a steel panel primed with analkyd primer and baked for 30 minutes at about 120° C. to give a glossy,hard finish with a good appearance. The finish was resistant toweathering, solvents, scratches and has excellent chip resistance. Theabove properties show that the coating composition is useful forfinishing cars and trucks.

The above composition when sprayed and baked did not sag. Controls thathad no star polymer produced sag when placed in the baking oven. Thisshows that the star polymers are useful in coatings.

EXAMPLE 24

This describes the use of star polymers as tougheners for plasticsheeting.

Dried star polymer (20.0 g), as prepared in Example 2 was dissolved in75.0 g of methyl methacrylate by heating to 55° C. for about 30 minutes.This solution was cooled to room temperature, and 5.0 g of a solution of50.0 g methyl methacrylate, 0.8 g of Lupersol 11 peroxide catalyst fromLucidol, and 0.080 g of Vazo 64 azobisisobutyronitrile polymerizationcatalyst from Du Pont were added. The resulting water white solution wasdegassed using an aspirator for 15 minutes.

The resulting solution was poured into a thermocoupled mold made from6.35 cm squares of 0.635 cm safety glass, held apart by a 0.317 cmgasket. The mold was immersed into an 80° C. water bath, and held 1hour. At 51 minutes a maximum mold temperature of 92.2° C. was recorded.

When the mold was removed it was placed in a 120° C. oven for 30minutes, then removed and cooled to room temperature.

The resultant casting was a clear strong sheet. This was cut into 2"squares and tested for impact strength using an instrumented impacttester with a Gardner-test geometry. Crack initiation energy for foursamples was determined to be 0.28±0.04 joules. Control samples madewithout the star polymer gave a result of 0.23±0.01 joules, whilecommercial clear poly(methyl methacrylate) sheet gave 0.17±0.06 joules.

These results show that the addition of a star polymer increased thestrength of a plastic part.

Industrial Applicability

In addition to the uses of star polymers of the invention in coatingsand as tougheners for plastic sheeting and in the other applicationsindicated above, such star polymers have many other potential uses, asdo other products made by group transfer polymerization. These caninclude cast, blown, spun or sprayed applications in fiber, film, sheet,composite materials, multilayer coatings, photopolymerizable materials,photoresists, surface active agents including soil repellants andphysiologically active surfaces, adhesives, adhesion promoters andcoupling agents, among others. Uses include as dispersing agents,rheology control additives, heat distortion temperature modifiers,impact modifiers, reinforcing additives, stiffening modifiers andapplications which also take advantage of narrow molecular weight andlow bimodal polydispersity. End products taking adavantage of availablecharacteristics can include lacquers, enamels, electrocoat finishes,high solids finishes, aqueous or solvent based finishes, clear or filledacrylic sheet or castings, including automotive and architecturalglazing and illumination housings and refractors, additives for oil andfuel, including antimisting agents, outdoor and indoor graphicsincluding signs and billboards and traffic control devices, reprographicproducts, and many others.

I claim:
 1. An arm/core process for preparing acrylic star polymerswhich comprisea. a crosslinked core comprising a polymer derived from amixture of monomers (A) comprisingi. 1-100% by weight of one or moremonomers each having at least two groups. ##STR35## ii. 0-99% by weightof one or more monomers, each having one group, ##STR36## b. attached tothe core, at least 5 arms comprising polymer chains derived from one ormore monomers (B), each having one group, ##STR37## in each of which Ris the same or different and is H, CH₃ C₃ CH₂, CN or CO₂ R' and Z' is Oor NR', wherein R'is C₁₋₄ alkyl, and c. attached to the core or to atleast some of the arms, living group transfer polymerization sites whichare (R¹)₃ M wherein; R is selected from the group consisting of C₁₋₁₀alkyl and C₆₋₁₀ aryl or alkaryl; and M is Si, Sn, or Ge,said processcomprising group transfer polymerization utilizing a tetracoordinateorganosilicon, organotin or organogermanium polymerization initiatorhaving at least one initiating site, and a catalyst suitable for grouptransfer polymerization, involving the sequential steps of a. preparinga living arm polymer by reacting the transfer initiator with one or moremonomers (B), each having one group ##STR38## b. contacting theresulting living polymers in the presence of the catalyst with a mixtureof monomers (A) comprisingi. 1-100% by weight of one or more monomerseach having at least two groups, ##STR39## ii. 0-99% by weight of one ormore monomers, each having one group, ##STR40##
 2. A core/arm processfor preparing acrylic star polymers which comprisea. a crosslinked corecomprising a polymer derived from a mixture of monomers (A) comprisingi.1-100% by weight of one or more monomers, each having at least twogroups. ##STR41## ii. 0-99% by weight of one or more monomers, eachhaving one group, ##STR42## b. attached to the core, at least 5 armscomprising polymer chains derived from one or more monomers (B), eachhaving one group, ##STR43## in each of which R is the same or differentand is H, CH₃, CH₃ CH₂, CN or CO₂ R' and Z' is O or NR', wherein R' isC₁₋₄ alkyl, and c. attached to the core or to at least some of the arms,living group transfer polymerization sites which are (R¹)₃ M wherein; Ris selected from the group consisting of C₁₋₁₀ alkyl and C₆₋₁₀ aryl oralkaryl; and M is Si, Sn, or Ge,said process comprising group transferpolymerization utilizing a tetracoordinate organosilicon, organotin ororganogermanium polymerization initiator having at least one initiatingsite, and a catalyst suitabe for group transfer polymerization,involving the sequential steps of a. preparing a living core polymer byreacting the transfer initiator in the presence of the catalyst with amixture of monomers (A) comprisingi. 1-100% by weight of one or moremonomers, each having at least two groups, ##STR44## ii. 0-99% by weightof one or more monomers, each having one group, ##STR45## b. contactingthe resulting living core polymer in the presence of the catalyst withone or more monomers (B) each having one group, ##STR46##
 3. Anarm/core/arm process for preparing acrylic star polymer which comprisea.a crosslinked core comprising a polymer derived from a mixture ofmonomers (A) comprisingi. 1-100% by weight of one or more monomers, eachhaving at least two groups. ##STR47## ii. 0-99% by weight of one or moremonomers, each having one group, ##STR48## b. attached to the core, atleast 5 arms comprising polymer chains derived from one or more monomers(B), each having one group, ##STR49## in each of which R is the same ordifferent and is H, CH₃, CH₃ CH₂, CN or CO₂ R' and Z' is O or NR',wherein R' is C₁₋₄ alkyl, and c. attached to the core or to at leastsome of the arms, living group transfer polymerization sites which are(R¹)₃ M wherein; R is selected from the group consisting of C₁₋₁₀ alkyland C₆₋₁₀ aryl or alkaryl; and M is Si, Sn, or Ge,said processcomprising group transfer polymerization utilizing a tetracoordinateorganosilicon, organotin or organogermanium polymerization initiatorhaving at least one initiating site, and a catalyst suitable for grouptransfer polymerization, involving the sequential steps of a. preparinga living arm polymer by reacting the transfer initiator with one or moremonomers (B), each having one group ##STR50## b. contacting theresulting living polymers in the presence of the catalyst with a mixtureof monomer (A) comprisingi. 1-100% by weight of one or more monomers(A), each having at least two groups, ##STR51## ii. 0-99% by weight ofone or more monomers, each having one group, ##STR52## c. contacting theresulting living star polymer with one or more monomers (C), each havingone group ##STR53## where the monomers (C) can be the same as ordifferent from the monomers (A).
 4. An arm/core process for preparingacrylic star polymers which comprisea. a crosslinked core comprising apolymer derived from a mixture of monomers (A) comprisingi. 1-100% byweight of one or more monomers each having at least two groups,##STR54## ii. 0-99% by weight of one or more monomers, each having onegroup, ##STR55## b. attached to the core, at least 5 arms comprisingpolymer chains derived from one or more monomers (B), each having onegroup, ##STR56## in each of which R is the same or different and H, CH₃,CH₃ CH₂, CN or CO₂ R' and Z' is O or NR', wherein R' is C₁₋₄ alkyl, andc. attached to the core or to at least some of the arms, living grouptransfer polymerization sites which are (R¹)₃ M wherein; R is selectedfrom the group consisting of C₁₋₁₀ alkyl and C₆₋₁₀ aryl or alkaryl; andM is Si, Sn, or Ge,said process comprising group transfer polymerizationutiizing a tetracoordinate organosilicon, organotin or organogermaniumpolymerization initiator having at least one initiating site, and acatalyst suitable for group transfer polymerization, involving thesequential steps of a. preparing a living arm polymer by reacting thetransfer initiator with one or more monomers (B), each having one group##STR57## b. contacting the resulting living polymers in the presence ofthe catalyst with a mixture of monomers (A) comprisingi. 1-100% byweight of one or more monomers each having at least two groups,##STR58## ii. 0-99% by weight of one or more monomers, each having onegroup, ##STR59## wherein the monomer of (a)(i) is methyl methacrylate,the monomers of (a) (ii) and (b) are ethylene glycol dimethacrylate, andthe group transfer polymerization is conducted using1-trimethylsiloxy-1-isobutoxy-2-methylpropene as the initiator andtetrabutyl ammonium bifluoride as the catalyst.